WARNING LIGHTS ABOVE 60 MPH

1995 Nissan Pathfinder

I have a 1995 Nissan Pathfinder, 6 cyl, with manual transmission and 140,000 miles on it. It rides fine below 60mph. From 60-70 mph the battery and brake warning indicators begin to intermittently flicker in unison. When they do, the headlights and dash lights dim, but there are no other indications of problems. Above about 75 mph, the two indicator lights stay on and all lights (dash and headlights) get very dim, then the engine starts to shudder as if it has no electrical power and wants to stall. It all gets better when I slow down below 60.
I tried revving the engine, mashing the clutch and bringing the rpms well above where they would be when driving 75 mph, but nothing unusual happens. Its only when I'm in gear and driving that this problem occurs. What's wrong with my Pathfinder?

Thanks ! I took a look at the fan belt and found that it WAS loose ! I tightened the belt and went for a test drive. Things SEEMED better but after everything warmed up and I got up to 75 mph the problem returned, though it did not appear as bad. I gave in and bought a remanufactured alternator, installed it, and had no problems on the second test drive. (When I started explaining the problem to the guy at the parts counter he finished my sentence for me with &quot. And the voltmeter goes crazy, right?&Quot; )

On closer inspection of the original alternator (before I returned it for the core charge refund) I found that the pulley was unusually worn, to the point that the inner walls had a mirror-like finish. Much more polished than normal wear on a typical pulley. I was tempted to put the old alternator back in and simply swap pulleys to see if that was the problem but guessed that if I did that, the alternator with 140,000 miles on it would fail me in the not so distant future and I'd be back under the hood a second time.

Why was the belt so loose in the first place? I had had the timing belt replaced at 100, 00 miles (40,000 miles ago). My guess is that the alternator fan belt had been loose since then. I had visually inspected everything at every oil change but had not physically pushed on that one belt since at least the time of the timing belt change.